A LISN (Line Impedance Stabilization Network) and 1uF capacitor was added to the Generalized Test Protocol for Calculating the Energy Efficiency of Internal AC-DC and DC-DC Power Supplies (Version 6.7.2). The addition of the 50µH LISN provides a known and stable input impedance when measuring the input power factor of very lightly loaded power supplies (below 20% loading) while the 1uF capacitor is used as a low pass filter. Testing at several labs, including OEM labs, showed that the power factor readings were much more repeatable when using the LISN and 1uF capacitor.

For the 115V and 230V EU Internal Non-Redundant test bench, the Yokogawa WT5000E is employed to monitor and measure various input parameters, including input voltage (V), input current (A), input frequency (Hz), input power (Watts), power factor (λ), and input current total harmonic distortion (THD %)

To accurately measure output voltage for desktop power supplies tested at both 115V and 230V EU input, we connect sense leads from the Chroma 63640-150-60 and 63610-80-20 electronic load banks directly to the rear of the output connectors using piercing probes. These probes interface with the back of the cable connector that connects to the load, ensuring voltage is measured as close to the load input as possible. Measurements are logged every second during the 15 minute steady-state period for each load condition.

We use three high-performance, programmable 3-phase AC power sources for testing:

230V EU Internal, Non-Redundant tests are conducted at 50 Hz. All other tests-115V Internal Non-Redundant, and 230V & 277/480V Internal Redundant (for North American servers) are conducted at 60 Hz, and 380V DC Internal Redundant- is conducted at 0 Hz

The input voltage measurement is taken as closely as possible to the unit's input connector. A C19 and C14 extractable cable is tailored for common input connectors to achieve this. This specialized input power cable is equipped with voltage measurement leads affixed to the input voltage wires within one-and-a-half-inch proximity to the unit's input power mating connector, as shown in Figure 1 and Figure 2.